423........thats a joke, nobody can answer that exactly, as matrix said, it depends on your marker and the exacct way you have it set up, velocity, temperature and ball to barrel match all play into it. but a 48/3000 is the smallist air tank you could possibly get, its probably the equivalent to a 9oz co2
after every game? thats fine, at the days end id take it off though, kinda depends on the marker but i dont like leaving that pressure on all the seals overnight or anyhting
68/4500 are pretty much the standard, they are generally around $100
air tanks (acually the regulators on the tank) generally come in 2 pressure ratings, high pressure (hp) or low pressure (lp), hp is usually around 700-800 psi output pressure, the same as co2 and lp is....well i forgot that one, a A-5 requires hp though